Load sensor for a vehicle electronic stability system

ABSTRACT

A method of controlling a three-wheeled vehicle comprises: determining a state of a load sensor associated with a portion of vehicle; selecting a first start mass when the load sensor is in a non-loaded state; selecting a second start mass when the load sensor is in a loaded state; determining at least one vehicle parameter during operation of the vehicle; determining a calculated mass based at least in part on the at least one vehicle parameter; determining an effective mass based at least in part on the calculated mass and a selected one of the first and second start masses; defining an output of an electronic stability system of the vehicle based at least in part on the effective mass; and controlling a stability of the vehicle using the output of the electronic stability system.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 13/553,153, filed Jul. 19, 2012, which is a continuation ofU.S. Pat. No. 8,260,535 B2, issued Sep. 4, 2012, the entirety of both ofwhich is incorporated herein by reference. The entirety of each of thefollowing documents is also incorporated herein by reference: U.S.Provisional Patent Application Ser. Nos. 60/547,092 (filed Feb. 25,2004), 60/547,089 (filed Feb. 25, 2004), 60/496,905 (filed Aug. 22,2004); U.S. patent application Ser. No. 10/920,226 (filed Aug. 18,2004); International Application No. PCT/US2006/017477 (filed May 5,2006); and U.S. Pat. Nos. 6,263,261 (issued Jul. 17, 2001); 6,324,446(issued Nov. 27, 2001); 6,086,168 (issued Jul. 11, 2000); 6,409,286(issued Jun. 25, 2002); 6,338,012 (issued Jan. 8, 2002); 6,643,573(issued Nov. 4, 2003); and 6,745,112 (issued Jun. 1, 2004).

FIELD OF THE INVENTION

The present invention relates to a vehicle with an electronic stabilitycontrol system based at least in part on the mass of the vehicle,passenger and cargo.

BACKGROUND

Small urban transport vehicles are convenient for the limited amount ofparking space they require. They also require less energy to move giventheir reduced mass. Small off-road vehicles are used on rougher terrainand offer similar advantages. Such vehicles typically have recumbentseats or a single straddle seat, like all-terrain vehicles (also knownas “ATVs”).

These light mass vehicles have three or four wheels. In the case of athree-wheeled vehicle, two different configurations are generally known.The first configuration has two wheels at the front and one wheel at theback. The second configuration has one wheel at the front and two wheelsat the back.

The height of the center of gravity (CG) of a vehicle has a significantinfluence on the dynamic stability of the vehicle. The vertical positionof the CG is measured as a distance from the ground when the vehicle isat rest. For a vehicle having a straddle seat, the elevated position ofthe seat generally results in a high CG. This is a factor thatparticularly affects the stability of a light mass vehicle using astraddle type seat. The position of the center of gravity also changesaccording to the presence and the driving position of the driver on thestraddle seat. The presence of a passenger also has a significant effectgiven that the additional mass of the passenger accounts for asignificant portion of the mass of the loaded vehicle.

Recumbent type seat vehicles are generally more stable since they have alower CG when loaded but they require additional space. Recumbent typeseats include bucket seats of the type usually found in four-wheeledvehicles. Recumbent seat configurations in a four-wheeled vehiclegenerally position two riders side-by-side.

While straddle seats may alter disadvantageously the center of gravityof a vehicle, they offer certain advantages that are not available withrecumbent seats. In particular, straddle seats allow the driver to adopta more compact riding position, allow for a better vision since thedriver is disposed higher, and permit the rider to lean into a turn forenhanced handling.

An advantage of a vehicle having a tandem straddle type seat, which canaccommodate a driver and a passenger behind the driver is that thecenter of gravity of the vehicle remains laterally symmetricallypositioned when the vehicle is upright regardless of whether a passengeris present or not. In contrast, on a light mass recumbent vehicle havingside-by-side seats, when only the driver is present, the center ofgravity is not laterally located in the same position as when there aretwo riders in the vehicle. When only a driver is present onboard avehicle with side-by-side recumbent seats, the center of gravity will beoffset from the longitudinal centerline of the vehicle in a directiontoward the driver. As would be appreciated by those skilled in the art,this offset may have an effect on the handling performance of theside-by-side recumbent seat vehicle.

Other factors that affect stability include the distance between thetires—the track width. On a vehicle, the wheel base refers to thedistance between the front tire(s) and the rear tire(s). The wheeltrack, on the other hand, refers to the distance between two tires onthe same axle. A larger distance between the tires (whether it be thewheel base or the wheel track) enhances the stability of the vehicle,but creates a larger vehicle, in terms of overall length and width, thatmay be less manoeuvrable because of the vehicle's increased size.

When operating any vehicle, especially a three-wheeled vehicle,stability is a concern during turning. When negotiating a curve, avehicle is subject to centrifugal forces, as is readily understood bythose of ordinary skill in the art of vehicle design. Generally, ahigher center of gravity causes the vehicle to have a lower rolloverthreshold than a vehicle with a lower center of gravity due tocentrifugal forces.

Three-wheeled vehicles raise special stability concerns since they havea smaller total footprint area with the ground than a similar sizedfour-wheeled vehicle. Also, three-wheeled vehicles tend to have asmaller mass. Therefore, they are also more affected by load variations,such as driver, passenger and cargo mass.

As would be appreciated by those skilled in the art, modern road tirescan offer considerable grip on a road surface. The gripping force ofmodern road tires can be so strong, in fact, that a vehicle with a highcenter of gravity may be subjected to centrifugal forces that may causethe vehicle to exceed its rollover threshold. If the rollover thresholdis exceeded, one or more of the vehicle's wheels on the inner side ofthe curve may lift off of the road surface, which may lead in somecircumstances to the vehicle rolling over. Rollover can also occur undersevere over steering conditions when the tires suddenly recover tractionwith the ground or hit an obstacle sideways.

For these reasons, Electronic Stability Systems (ESS) have beendeveloped to improve the stability of such vehicles.

ESS, also known as Vehicle Stability Systems (VSS), are designed toelectronically manage different systems on a vehicle to influence andcontrol the vehicle's behaviour. An ESS can manage a considerable numberof parameters at the same time. This provides an advantage over avehicle having no such system since the driver can only manage a limitednumber of parameters at the same time and has a slower reaction time. Atypical ESS takes several inputs from the vehicle and applies differentcorrective measures back to the vehicle to influence the vehicle'sbehaviour. Examples of inputs include steering column rotation,longitudinal and transverse acceleration of the vehicle, engine output,brake and accelerator pedal displacement, rotational speed of thewheels, and brake pressure in the brake system amongst others.

The outputs from the ESS affect the vehicle's behaviour generally byindependently managing the brakes on each wheel, the suspension, and thepower output of the engine in order to improve the vehicle's handlingunder certain circumstances.

However, since the load (rider, passenger, cargo mass) applied to lightmass vehicle has a significant impact on its handling characteristics,as previously mentioned, the ESS may take insufficient correctivemeasures when the vehicle is heavily loaded or may unnecessarily limitthe vehicle performance when the vehicle is lightly loaded depending onthe ESS calibration.

Therefore, there is a need for a system that controls the stability of alight mass vehicle that takes into consideration the overall mass of thevehicle (vehicle, driver, passenger).

SUMMARY

It is an object of the present invention to ameliorate at least some ofthe inconveniences present in the prior art.

In one aspect, a method of controlling a three-wheeled vehicle isdisclosed. The three-wheeled vehicle has a frame, three wheels attachedto the frame; and a straddle seat supported by the frame. The straddleseat defines a driver portion and a passenger portion adjacent to thedriver portion. The method comprises: determining a state of a loadsensor associated with a portion of vehicle; selecting a first startmass when the load sensor is in a non-loaded state; selecting a secondstart mass when the load sensor is in a loaded state; determining atleast one vehicle parameter during operation of the vehicle; determininga calculated mass based at least in part on the at least one vehicleparameter; determining an effective mass based at least in part on thecalculated mass and a selected one of the first and second start masses;defining an output of an electronic stability system of the vehiclebased at least in part on the effective mass; and controlling astability of the vehicle using the output of the electronic stabilitysystem.

In a further aspect, the first start mass is based on adriver-and-vehicle combined mass, and the second start mass is base onea driver-and-passenger-and-vehicle combined mass.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle includes determining an acceleration ofthe vehicle.

In a further aspect, determining the acceleration of the vehicleincludes obtaining the acceleration of the vehicle from a longitudinalaccelerometer of the vehicle.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle further includes determining a torqueprovided by an engine of the vehicle. The calculated mass is determinedbased on the acceleration of the vehicle and the torque provided by theengine.

In a further aspect, the calculated and effective masses are notdetermined when the acceleration of the vehicle is outside of apredetermined range.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle includes determining a torque providedby an engine of the vehicle.

In a further aspect, determining the torque provided by the engine ofthe vehicle includes: obtaining a degree of throttle opening from athrottle position sensor; and obtaining a speed of the engine from anengine speed sensor.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle includes determining a deceleration ofthe vehicle.

In a further aspect, determining the deceleration of the vehicleincludes obtaining the deceleration of the vehicle from a longitudinalaccelerometer of the vehicle.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle further includes determining a braketorque. The calculated mass is determined based on the deceleration ofthe vehicle and the brake torque.

In a further aspect, the calculated and effective masses are notdetermined when the deceleration of the vehicle is outside of apredetermined range.

In an additional aspect, determining the at least one vehicle parameterduring operation of the vehicle includes determining a brake torque.

In a further aspect, determining the brake torque includes obtaining abrake pressure from a brake pressure sensor.

In an additional aspect, the method further comprises determining if thevehicle is turning. The calculated and effective masses are notdetermined when the vehicle is turning.

In a further aspect, determining if the vehicle is turning is based onan input from a steering angle sensor.

In an additional aspect, determining the effective mass includes:determining a difference between the calculated mass and the selectedone of the first and second start masses; determining a percentage ofthe difference to be applied to the selected one of the first and secondstart masses; adding the percentage of the difference to the selectedone of the first and second start masses when the calculated mass isgreater than the selected one of the first and second start masses;subtracting the percentage of the difference from the selected one ofthe first and second start masses when the calculated mass is smallerthan the selected one of the first and second start masses.

In a further aspect, the method further comprises repeating the steps ofdetermining the at least one vehicle parameter, the calculated mass andthe effective mass over a number of iterations. The percentage of thedifference to be applied to the selected one of the first and secondstart masses increases as the number of iterations increases.

In an additional aspect, the method further comprises validating thestate of the load sensor when the load sensor is determined to be in aloaded state by applying a delay after the load sensor is determined tobe in a loaded state.

For purposes of the application, terms related to spatial orientation,such as “left”, “right”, “front”, “rear”, “up”, and “down”, are definedaccording to the normal, forward travel direction of a vehicle. As aresult, the “left” side of a vehicle corresponds to the left side of arider seated in a forward-facing position on the vehicle.

Embodiments of the present invention each have at least one of theabove-mentioned objects and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presentinvention that have resulted from attempting to attain theabove-mentioned objects may not satisfy these objects and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects, and advantages ofembodiments of the present invention will become apparent from thefollowing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a left side elevation view of a three-wheeled vehicleaccording to one embodiment of the present invention;

FIG. 2 is a top plan view of the three-wheeled vehicle of FIG. 1;

FIG. 3 is a schematic diagram depicting a plurality of sensors and aplurality of outputs associated with an Electronic Stability Systemaccording to one embodiment of the present invention;

FIG. 4 is a longitudinal cross-sectional view of a straddle seat havinga passenger seat sensor according to one embodiment of the presentinvention;

FIG. 5 is a bottom plan view of the straddle seat of FIG. 4;

FIG. 6 is a close-up view of longitudinal cross-sectional view of FIG.4;

FIG. 7 is a diagram showing a mass estimation strategy according toanother one embodiment of the present invention;

FIG. 8 is a diagram showing a mass estimation strategy according to oneembodiment of the present invention;

FIG. 9 is a diagram showing a mass estimation strategy according to yetanother embodiment of the present invention;

FIG. 10 is a diagram showing a mass estimation strategy according toanother embodiment of the present invention;

FIG. 11 is a calibration of the engine torque associated with variousvalues from a throttle position sensor and various engine RPM accordingto one embodiment of the present invention;

FIG. 12 is a diagram illustrating the brake torque applied on the wheelsof the vehicle in relation with hydraulic brake pressure according to another embodiment of the present invention;

FIG. 13 is a logic diagram illustrating the strategy of FIG. 10;

FIG. 14 is a diagram illustrating hydraulic brake pressure ramp-up speedin function of the mass of the vehicle according to the presentinvention; and

FIG. 15 is a diagram illustrating hydraulic brake pressure in functionof the mass of the vehicle according to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. Each example is provided by way of explanation ofthe invention, not limitation of the invention. It will be apparent tothose skilled in the art that modifications and variations can be madeto the described embodiments without departing from the scope or spiritof the invention. For instance, features illustrated or described aspart of one embodiment may be used on another embodiment to yield afurther embodiment.

A three-wheeled straddle-type vehicle 10 in accordance with the presentinvention is generally illustrated in FIGS. 1-3. The vehicle 10 has alongitudinal axis and includes a left front wheel 14, a right frontwheel 16 and a rear wheel 18. The front wheels 14, 16 are equally offsetfrom the longitudinal axis, and the rear wheel 18 is aligned with thelongitudinal axis. The left and right front wheels 14, 16 and the rearwheel 18 each have a tire. The rear wheel 18 may include multiple rims,with each rim accommodating a tire. In the case of a multi-rimarrangement, the rims would be rigidly connected to form a single wheel.For purposes of simplicity, when the rear tire is referred to in thisapplication, it will be understood that the rear tire may includemultiple tire components mounted on individual rims but acting as asingle wheel.

The tires have a friction coefficient in accordance with the tiremanufacturer's specifications. Each of the wheels 14, 16 and 18 is sizedto accommodate a 15-inch automobile tire for example. The presentinvention, however, is not limited to equal sized wheels; rather, it iscontemplated that the front wheels 14, 16 may be smaller in size toaccommodate 13-inch automobile tires for example. Furthermore, otherwheel sizes are considered to be well within the scope of the presentinvention.

The front wheels 14, 16 are supported by a front suspension assembly 26.The rear wheel 18 is supported by a rear suspension assembly 28. Thefront suspension assembly 26 and the rear suspension assembly 28 aresecured to a vehicle frame assembly 12 illustrated in FIG. 1. The frontsuspension assembly 26 illustratively includes a pair of suspensionsupport arms (A-arms) and a shock absorber extending from each side ofthe frame assembly 12 to support each front wheels 14, 16. The rearsuspension assembly 28 illustratively includes a rear swing arm assemblythat is attached to the frame assembly 12 by an axle that extendsthrough the frame assembly 12.

As shown in FIG. 1, the rear swing arm assembly includes a rear swingarm 28 that is pivotally supported by an axle, which is retained in apivot bore to the frame 12. The swing arm 28 is formed in a generallyU-shape with a pair of parallel arm portions, that extend rearwardlyfrom the front pivot axis of the swing arm 28 to the rear tires. Therear swing arm 28 is suspended from the frame assembly 12 and is biasedby a shock absorber and spring assembly. By this arrangement, the rearwheel 18 has a controlled range of pivotal movement about a lateral axiswith respect to the frame assembly 12.

As illustrated in FIG. 1, the outer side of the frame spar is visiblefrom the left side of the vehicle 10. Preferably, the frame assembly 12is a tubular frame, with at least some of the frame elements beingformed of tubular members. The tubular members can have any crosssection, including but not limited to square, rectangular, circular,oval and channel shaped. As such, tubular members contemplated by thisinvention include both closed and open cross sections, which may be madeby casting, forging, stamping, or extrusion. The advantage of tubularmembers is that such elements are very strong, yet lightweight. Anengine 30 is secured to the vehicle frame assembly 12 adjacent to anengine cradle assembly 13. The engine 30 may be secured directly to theframe assembly 12 at several points of attachment. Alternatively, theengine 30 may be secured to the frame assembly 12 using a suitablemounting assembly, not shown. The engine 30 can be a structural elementof the frame assembly 12 adding rigidity. Alternatively, the engine 30may be merely supported by the frame assembly 12.

The engine 30 is supported just behind the front suspension assembly 26immediately above the lowest part of the frame assembly 12. Thispositioning provides a low center of gravity, which is useful inensuring good handling and stability of the vehicle 10. Because of therigidity and structural strength of the frame assembly 12, the engine 30can generate 50-150 horsepower or more without sacrificing stabilityand/or manoeuvrability of the vehicle 10. The frame assembly 12 providessufficient structural rigidity to withstand the forces created duringhigh performance operation of the vehicle 10. The engine 30illustratively is an internal combustion engine and is preferably afour-stroke engine. In particular, the engine 30 may be a 1000 cc V-twin(V2) four-stroke engine manufactured by ROTAX®. The vehicle 10 inaccordance with the present invention, however, is not limited to a 1000cc engine. It is also contemplated that a 600 cc engine may be used.Furthermore, other engine displacement sizes are considered to be wellwithin the scope of the present invention. Moreover, while a four-strokeengine is contemplated for use on the vehicle 10, a two-stroke enginealso may be employed. Alternatively, hybrid powerpack or electric motorcould also power the vehicle without departing from the scope of thepresent invention.

The engine 30 is preferably connected to a manual speed transmissionwith a clutch in a manner similar to those available on typicalmotorcycles. Alternatively, the three-wheeled vehicle 10 may use a CVT.Other types of transmissions are contemplated and remain within thescope of the present invention.

A fender assembly 40 is associated with each of the front wheels 14, 16.The fender assembly 40 prevents dirt, water and road debris from beingthrown up onto the rider, while the rider operates the vehicle 10. Eachfender assembly 40 is linked to the front suspension assembly 26 and asteering assembly 34 such that the fender assemblies 40 move with thewheels 14 and 16 during steering of vehicle. This arrangement ensuresthat the tires will not throw dirt, water and road debris at theoperator as the vehicle 10 turns. Each fender assembly 40 preferablyincludes a turn signal 42 located on the top surface of fender assembly40, as shown in FIGS. 1 and 2.

The steering of the front wheels 14 and 16 is accomplished through theuse of the steering assembly 34. The steering assembly 34 includeshandlebars 32 and steering linkages (not shown) connected to the wheels14 and 16 for purposes of turning the wheels 14 and 16 in response tomovement of the handlebars 32. The steering assembly 34 of the vehicle10 is preferably provided with a progressive steering system (notshown).

The front of the vehicle 10 includes a fairing assembly 36, whichencloses the engine 30 to protect it and to provide an external shellthat can be decorated so that the vehicle 10 is aesthetically pleasing.The fairing assembly 36 is preferably made from fibreglass having a gelcoat, although other materials including plastic are considered to fallwithin the scope of the invention. The fairing assembly 36 includes anupper portion, a hood removably secured to the upper portion and abottom pan. The fairing assembly 36 is secured to the vehicle frameassembly 12 by a plurality of fairing anchors.

The vehicle 10 of FIG. 1 is designed with a straddle-type seat assembly20 that preferably accommodates two adult-sized riders, a driver and apassenger. Thus, the seat assembly 20 defines a driver portion 22 and apassenger portion 24 behind and adjacent the driver portion 22. Whilethe vehicle 10 is not designed to accommodate more than two adult-sizedriders, the present invention contemplates that the design of vehicle 10may be changed easily to accommodate more than two adult-sized riders.The vehicle 10 includes a cushioned rider seat assembly 20 that ismounted to the frame assembly 12 between the front wheels 14 and 16 andthe rear wheel 18, as shown in FIGS. 1 and 2. The seat assembly 20 isconnected to the vehicle frame assembly 12 with a seat support assembly172. The seat assembly 20 is positioned so that the mass of the riderthereon will be disposed generally above the suspension 28 of the frameassembly 40. Consequently, the mass of the rider will be transferredthrough the seat assembly 20 and frame assembly 12 to the rearsuspension assembly and the rear swing arm 28 and to the frontsuspension assembly 26.

Still referring to FIG. 1, it can be seen that the center of gravity 52of a driver sitting on the driver seat portion 22 in a normal sittingposition looking forward with legs on each side of the vehicle is lowerthan the center of gravity 54 of a passenger sitting on the passengerseat portion 24 in a normal sitting position looking forward with legson each side of the vehicle. The combined center of gravity 56 of thevehicle with only a driver is lower than the combined center of gravity58 of the vehicle with a driver and a passenger. The additional massprovided by a passenger on the vehicle has a significant effect on theoverall mass of the vehicle. This increased mass with the higher centerof gravity 58 has a significant effect on the stability and the dynamicbehaviour of the vehicle and therefore must be monitored and used whencalculating the corrective measures.

Vehicle 10 is equipped with an Electronic Stability System (ESS) 140(FIG. 3) which continuously monitors different vehicle parameters andapplies corrective measures, i.e. wheel braking and/or engine torquemanagement, whenever the vehicle parameters indicate the vehicle is inan unstable state. The ESS, mounted onboard vehicle 10, usespredetermined calibration data commonly disposed on a graph (or mapping)to determine which outputs (i.e. corrective measures) should be providedgiven specific inputs based on the vehicle parameters, one of which isthe mass of the combined vehicle and passenger. The magnitude and thetiming of the outputs are also managed by the ESS 140 in order to applythe appropriate corrective measures to the vehicle 10. In the presentinvention, the term calibration is used to describe a mathematicalformula, a map, an algorithm or a value used to determine the outputs ofthe ESS based on the inputs.

The ESS 140 is dependent on inputs provided by sensors sensing thevehicle's behaviours to determine what are the right outputs to begenerated. A series of sensors can be used for sensing differentphysical properties, as shown on FIG. 3. This list of sensors is forillustrative purposes and does not intend to limit the scope of thisapplication to the listed sensors but to all state of the art sensors inthe automotive field. Published United States patent application numberUS 2006/0180372A1, filed Aug. 18, 2004 and assigned to the same assigneeprovides more information about an ESS 140 and related sensors and isenclosed herewith by reference.

In the present embodiments, there are four sensors 100, 102, 104 and 106to accommodate a four-wheeled vehicle (not shown). Two sensors can beused on the same wheel when an ESS 140 designed for a four-wheeledvehicle is used with a three-wheeled vehicle 10. Steering angle sensor108 provides information about the angular position of the steeringassembly 34 from which can also be determined the steering angle rate(e.g. the speed at which the steering is rotated). Lateral andlongitudinal acceleration sensors 110, 112 are in communication with theESS 140 and provide information about the lateral and longitudinalaccelerations of the vehicle 10. These accelerometers 110, 112 can becombined with a yaw rate sensor 114 sensing the yaw rate of the vehicle10 about a vertical axis in addition to longitudinal and lateralaccelerations.

A seat sensor 118 (or passenger load sensor) is installed in thepassenger seat portion 24 to send signals to the ESS 140 about thepresence or the absence of a passenger sitting on the vehicle 10. Thissensor 118 will be discussed in greater detail below. A cargo sensor120, substantially performing the same role as the seat sensor 118, isinstalled on the vehicle 10. For example, cargo can be put in storagecompartment (not shown) disposed on the rear portion of the vehicle 10.The cargo sensor 120 can determine the presence of cargo and/orquantitatively determine how much load there is present in thesaddlebags by using a strain gage or similar technology. A suspensionsensor 122 provides information to the ESS 140 about the suspensiondeflection (or the height of the vehicle) based on the instant positionof the suspension along the overall suspension travel to determine themass supported by the suspension. It is well known that a springcompresses linearly according to the force applied to it, therefore themass applied on the suspension can be deducted from the deflection ofthe suspension. Common linear position sensors can be used to monitorthe suspension position.

A brake pressure sensor 116 informs the ESS 140 of the instant amount ofpressure in the brake system. Many brake pressure sensors 116 can berequired to monitor different portions of the hydraulic brake system;i.e. the front and rear brake systems. A brake light switch 124 sends asignal to the ESS 140 when the brakes are activated, even lightly,regardless of the amount of pressure generated in the brake system. Abrake fluid level sensor 126 is installed in each brake fluid reservoiron the vehicle 10 and provides information on the brake fluid level tothe ESS 140. A brake travel sensor 128, adapted to sense the brakeactuator position, indicates hard braking from the driver to the ESS140. The brake travel sensor 128 is activated after the brake lightswitch 124 to determine, for example, strong intentional brake actuationor extreme brake lever movement due to a loss of brake fluid pressure inthe brake system.

An engine RPM sensor 130 informs the ESS of the rotational speed of theengine 30. A throttle position sensor 132 (TPS) determines how much thethrottle is opened to allow air inside the combustion chamber of theengine 30; the throttle opening being calculated between 0° and 90°. Amass air flow sensor 134 indicates how much air is travelling throughthe throttle. All these sensors are well known in the art and will notbe discussed in detail in this application. These sensors can be usedindividually or collectively to bring inputs usable by the ESS 140 toanalyze the vehicle's behaviour such that appropriate outputs can beapplied to the vehicle 10.

Various outputs might be provided by the ESS 140 to influence thebehaviour of the vehicle 10. The ESS 140 can send outputs to increasethe brake pressure 150 (FIG. 15) in the brake system, thus forcingbraking of the vehicle 10 by overriding manual actuation of the brakeactuator from the driver. The ESS 140 can also increase or decrease thebrake pressure ramp-up 152 (FIG. 14). The brake pressure ramp-up 152 isthe speed at which the brake fluid pressure is raised to brake thevehicle 10 therefore providing a stronger and faster braking to thevehicle 10. Another output from the ESS 140 could be used to increase ordecrease the stiffness 154 of the steering assembly 34. Change in thepower output 156 of the engine 30 is normally done by the ESS 140through the electronic control unit 158 (ECU) controlling the engine 30.The ECU 158 electronically modifies, individually or collectively, theignition timing, the fuel injection timing and the amount of fuelinjected in the combustion chamber.

Referring to FIG. 4, a left side elevation section view of the seatassembly 20 with the driver seat portion 22 and the passenger seatportion 24 is shown. A driver backrest 174 separates the driver seatportion 22 from the juxtaposed passenger seat portion 24. The passengerseat portion 24 is ending with a passenger backrest 176 to providesupport for the passenger when the vehicle 10 accelerates. The seatassembly 20 is constituted of a seat support assembly 172 on which issuperposed a volume of foam 170 protected by a seat cover 178. A seatsensor 118 for sensing the presence or the absence of a passengersitting on the passenger seat portion 24 is located in the seat assembly20. It is attached to the seat support assembly 172 in the areasupporting the mass 171 of a passenger sitting on the passenger seatportion 24. The seat sensor 118 could alternatively be fixed on theframe 12 of the vehicle 10 and fit into an opening in the bottom of theseat assembly 20 installed on the vehicle 10 without departing from thescope of the present invention. This arrangement would prevent damagingthe seat sensor 118 when the seat assembly 20 is removed from thevehicle 10.

FIG. 5 depicts a bottom plan view of the seat to show the position ofthe seat sensor 118 on the seat support assembly 172 with respect to thesitting position of a passenger on the passenger seat portion 24. Theseat sensor 118 is preferably disposed in such a position 171 that theright sitting bone (one of the ischia bones of the passenger) iscompressing the foam 170 just above the seat sensor 118. The alignmentwith a sitting bone ensures good mass transfer from the passenger to theseat sensor 118 (other seat sensor 118 positions in respect to thepassenger sitting on the seat could work, however relying on the fleshof the passenger to activate the seat sensor 118 might be less precise).The seat sensor 118 is located to catch the mass of the right sittingbone in the present embodiment; however, the sensor could be located onthe left side 171.1 of the seat 20 without departing from the scope ofthe invention.

In the illustrated embodiment, the seat sensor 118 is a Hall Effect seatswitch provided by Delta Systems Inc. (part no. 6540-003 7AL). It can beappreciated from FIG. 6 that the moveable cover 202 of the seat sensor118 is in contact with the bottom portion of the foam 170 in the seatassembly 20. Pressure applied on the seat assembly 20 will compress thefoam 170 and will progressively activate the seat sensor 118. Pressureof the foam 170 on the vertically moveable cover 202 applies movement tothe vertically moveable stem 204 enclosed in the seat sensor 118. Themovement of the stem 204 alters the magnetic field of the Hall Effectportion 208 inside the seat sensor 118, hence changing the outputvoltage passing through wires 212 to the ESS 140. In the illustrativeembodiment, the output voltage can fluctuate between 0 Volts and 5Volts. The passenger presence is represented by the seat sensor 118 witha small voltage range, illustratively between 0.9 and 1.85 Volts. Incontrast, the passenger absence is represented with a distinct voltagerange, illustratively between 2.5 and 4.15 Volts. End voltages are usedto determine faulty connections of the seat sensor 118. A voltage outputof less than 0.5 Volts means the circuit is open or shorted to ground.Conversely, a voltage of more than 4.9 Volts is interpreted by the ESS140 as being shorted to the battery. Remaining unassigned voltage rangesare safety intermediate positions. A classic on/off contact switch isalso contemplated although it offers less flexibility than a Hall Effectsensor.

The ESS 140 uses some strategies to avoid misinterpreting the signalfrom the seat sensor 118. A time delay is applied before considering achange in the state of the sensor (e.g. from the passenger absenceposition to the passenger presence position and vice-versa). This helpsprevent unintentional change in state of the seat sensor 118 like apassenger momentarily putting more mass on the footrests and unloadingthe seat. Foam density and thickness of the seat is also designed suchthat a minimum mass is required before the seat sensor 118 is activated.In the present situation, the foam thickness is smaller above the seatsensor 118 than elsewhere on the seat to make sure the sensor 118 willbe activated when a predetermined pressure is applied on the seat. Aminimum mass of about 10 kilograms is required before the seat sensor118 gets into the passenger presence state.

The ESS 140 uses predetermined calibrations stored on a computerreadable media inside the ESS 140. The data can be updated by connectingthe ESS 140 on Internet through a computer to download into the ESS 140.Alternatively, the ESS 140 can use its Input/Output port to downloadupdated calibrations. The calibration is used for determining outputsbased on the inputs received from at least some of the plurality ofsensors. One fundamental input is the actual total mass of the vehicle10. The calibration is selected in function of the mass of the vehicle10 to ensure the strength and timing of the outputs are correspondingwith the overall mass of the vehicle 10. Each calibration is adapted toa different mass of the vehicle 10. Since no actual mass is provided tothe ESS 140 at start-up, a start mass 232 will be used to define any ESS140 outputs shortly after the vehicle begins to move. In a firstembodiment, the start mass 232 is an estimation of the complete mass ofthe vehicle 10 with a driver. This start mass 232 is unlikely toaccurately represent the actual exact mass of the vehicle 10 with thedriver due to the different people who will use the vehicle and thecargo each will wish to bring with them. It is therefore likely to leadthe ESS 140 to provide outputs that are either over or bellow what isreally required by the actual exact mass of the vehicle 10 and maynegatively affects the vehicle's behaviour.

The first embodiment is depicted by FIG. 7, one strategy consists inusing a start mass 232 that is an estimated mass of a fully loadedvehicle 10 (oil, gas, coolant, etc.) with a driver, a passenger and evena bit of additional cargo. This start mass 232 is used by the ESS 140 tocalculate any initial corrective measures needed. A person skilled inthe art can readily understand the ESS 140 is unlikely to provideappropriate outputs if the vehicle is more heavily loaded with a heavierpassenger and a lot of cargo. Conversely, the ESS 140 will provide toostrong corrections to the vehicle in the case of a light driver with nopassenger and therefore adversely affect the vehicle's performance. Thecorrecting measures provided by the ESS 140 must preferably take thismass variation into consideration. A more accurate total mass estimationis desirable in order for the ESS 140 to apply the correct measureswhich do not render the vehicle less performant nor too aggressive.

Still referring to FIG. 7, one would appreciate that the start mass 232has a significant effect on the performance of the vehicle. To make surethe vehicle is safe when a heavy driver and a heavy passenger with cargoare onboard, the start mass 234 should be increased as indicated in asecond embodiment illustrated in FIG. 8. In this scenario, the ESS 140outputs will safely take into consideration the possible heavy mass ofthe vehicle 10. The start mass 234 should be high enough to ensureadequate safety, although, in turn, the ESS 140 will significantlyreduce the performance of the vehicle, even if only a single lightdriver is onboard the vehicle is stable in all riding conditions.

For this reason, it is better to have two start masses 234, 236, asshown in FIG. 9 illustrating a third embodiment. This ensures sufficientsafety when the vehicle 10 accommodates both a driver and a passengerand significantly reduces the adverse effects on the vehicle'sperformance if only a driver is detected on the vehicle 10. Thepassenger seat sensor 118 is used to determine the presence or theabsence of a passenger on the passenger seat portion 24 of the vehicle10. In other words, if the passenger seat sensor 118 is in the passengerabsence position, a first calibration, having a start mass 236, would beused. The start mass 236 is estimated to be close to the maximum massallowed for vehicle 10 with a single driver. Start mass 236 is alsoupdated with continuously calculated mass changes 230 on both theheavier and the lighter sides. This way the vehicle 10 will providemaximum performance while preventing exceeding the safe handlingthreshold.

On the other hand, if the vehicle 10 supports both a driver and apassenger, the passenger seat sensor 118 is in the passenger presenceposition. A second calibration having a start mass 234 is used takinginto account that the vehicle supports a passenger and is therefore moreheavily loaded. The start mass 234 is estimated to be close to themaximum mass allowed for vehicle 10 with a driver and passenger. Startmass 234 will also be uploaded with continuously calculated mass changes230 on both the heavier and the lighter sides. This way, the ESS 140will provide maximum safety and will prevent exceeding the safe handlingthreshold.

With the information provided by the passenger seat sensor 118 and theuse of various start masses 236, 234, it is possible to provide adequatevehicle safety while not adversely affecting the performance of thevehicle 10.

Strategies can be used to improve the accuracy of the start masses 236and 234 during vehicle operation. One strategy uses the well-knownformula “F=m·a” to obtain a calculated mass 231 where “F” is a force inNewton, “m” is a mass in kilogram and “a” is an acceleration in“m/(s²)”. The ESS 140 uses either the vehicle's accelerations ordecelerations to define the variable “a” and deduct a calculated mass231 of the vehicle 10. We will first discuss using the acceleration.

The ESS 140 senses the throttle opening with the Throttle PositionSensor 132 and the RPM of the engine 30 with the engine RPM sensor 130.Then the ESS 140 refers to a calibration as seen on FIG. 10, todetermine the torque provided by the engine 30 under such throttleopening condition and engine RPM. This torque has been experimentallycalibrated according to various TPS positions and engine RPM as shown inFIG. 11. The ESS 140 uses the torque “τ” obtained from the calibrationand divides it by the radius “r”, in meters, of the wheel of the vehicle(and, if needed, taking into account any relevant transmission ratio) toget a force “F” in “Newtons” (τ=F·r therefore F=τ/r). The ESS 140 alsohas data on the acceleration “a” of the vehicle in “m/s²” provided bythe longitudinal accelerometer 112. The equation “F=m·a” is then appliedto isolate the mass “m” (m=F/a), that is the calculated mass 231.Iterations of this calculated mass 231 according to real life dataperiodically recalculate the calculated mass 231 to ensure its accuracy.The calculated mass 231 must be reliable because it influences the startmass 236 by increasing or decreasing the start mass 236. The calculatedmass 231 provides the ESS 140 with a more accurate total mass estimationof the vehicle 10 for determining the most accurate outputs from the ESS140.

The same principle is used in the case of decelerations although theinputs used to adjust the start mass 236 are different. In the case of adeceleration, the ESS 140 senses the brake pressure with the brakepressure sensor 116. Similarly, the brake pressure has previously beenexperimentally calibrated as provided by FIG. 12. For a given pressurein the hydraulic system, the ESS 140 determines a brake torque in “N·m”and divides it by the radius of the wheel, in meters “m”, to obtain aforce in “Newtons”. The ESS 140 also has data on the deceleration “a” ofthe vehicle obtained by the longitudinal accelerometer 112. Again, theequation “F=m·a” is applied to isolate the mass “m” (m=F/a). Iterationsof this calculated mass 231 according to real inputs influences thestart mass 236 by increasing or decreasing the start mass 236. Thecalculated mass 231 provides the ESS with a more accurate total massestimation of the vehicle 10 for determining the most accurate outputsfrom the ESS 140.

In other words, the ESS 140 uses a start mass 236 that is a fixeddefault value. A safe calculated mass 231 is obtained by the ESS 140 byanalysing the inputs in real time based on the vehicle's behaviours. Theexact overall mass of the vehicle is somewhere in between.

Further calculated mass 231 estimation iterations will adjust theselected start mass 234, 236 toward an even more accurate mass. Theiterations are made by the ESS 140 only when conditions are favourableto get a reliable calculated mass 230. For example, the ESS 140 does notget inputs for analysing the mass of the vehicle 10 when the vehicle 10is negotiating a curve based on the input from the steering angle sensor108. Strong and weak accelerations/decelerations are also not consideredbecause of the increased risk of errors.

Referring to FIG. 10, a calibration is depicted where the number ofiterations validating the calculated mass 231 is another factor takeninto consideration during this iterative mass adjustment process. Thehigher the number of iterations, the more accurate the calculated mass231 is considered to be. For example, a very small percentage of themass difference between the start mass 236 and the calculated mass 231is applied to the start mass 236 after one iteration. The portion of thedifference between the calculated mass 231 and the start mass 236 isadded or subtracted from the start mass 236 to define an effective mass233 subsequently used by the ESS 140 to determine the right correctivemeasures. The percentage of the mass difference applied to the mass usedby the ESS 140 (either the start mass 236 on the first iteration or theeffective mass 233 on subsequent iterations) increases with the numberof iterations. The higher the number of iterations, the bigger thepercentage of the mass difference is applied to the mass used by the ESS140. Only a slight change will be made to the start mass 236 during thefirst calculated mass iteration no matter how significant the calculatedmass 231 differs from the start mass 236. After many iterations, forexample five hundred (500), the effective mass 233 will be mostlyreplaced with the calculated mass 231. This is another safety measure toprevent any possibility of applying an erroneous mass to the ESS 140.This also shows that a certain amount of time is needed under favourableoperating conditions before a reliable mass is calculated. Thisillustrates the advantages of having a start mass when the vehiclebegins to move. It also illustrates the advantages of having a seatsensor 118, which provides an indication to the ESS 140 to use a secondstart mass 236 which is closer to the actual mass with the passenger(s).It is also contemplated that for a given sensor 118 output, a value isadded to the first mass representing an added mass to the vehicle 10.Depending on the sensor 118 output, different values can be added to thestart mass 236 to indicate riders of different mass seating on thevehicle 10.

FIG. 13 illustrates a flow chart referring to FIG. 10 indicating onepossible logic from the moment the seat sensor 118 state is sent to thecalculated mass 231 iterations. The ESS 140 senses the state at step 240of the seat sensor 118 (or load sensor). A delay is applied at step 244to validate the state of the seat sensor 118 if the presence of apassenger is detected at step 242 to prevent the ESS 140 to act upon awrong input. The calibration is selected at step 246 and start mass 234is used at step 248 by the ESS 140 to calculate the right correctivemeasures to be applied. The ESS 140 will begin to determine thecalculated mass 231 using successive iterations if the conditions aresatisfied at step 250. If the iteration conditions are not satisfied atstep 250, the ESS 140 will continue reusing the start mass 234. If theiteration conditions are satisfied, the ESS 140 will determine at step254 the new calculated mass 231 and will increase the iteration counterat step 256. An applicable percentage of the mass difference between thecalculated mass 231 and the start mass 234 will be determined at step258 by the number of successful iterations performed by the ESS 140. Theapplicable percentage of the mass difference will be added or subtractedto the start mass 234 to become the effective mass 233. The higher thenumber of iterations, the larger the portion of the mass difference isapplied, at step 260, to the start mass 234. If the iteration conditionsat step 250 are still respected, a new iteration will occur and thecycle continues until the iteration conditions at step 250 are not met,at which point the last effective mass calculated will be used.

In contrast, if the ESS 140 senses the state at step 240 of the seatsensor 120 and the presence of a passenger is not detected at step 270 adelay is also applied at step 272 to validate the state at step 274 ofthe seat sensor 118 to prevent the ESS 140 to act on a wrong input. Thecalibration is selected at step 276 and start mass 236 is used at step278 by the ESS 140 to determine the right outputs to be applied. The ESS140 will begin to determine the calculated mass 231 using successiveiterations if the conditions are satisfied at step 282. If the iterationconditions are not satisfied at step 282, the ESS 140 will continuereusing the start mass 236. If the iteration conditions are satisfied,the ESS 140 will determine at step 284 the new calculated mass 231 andwill increase the iteration counter at step 286. An applicablepercentage of the mass difference between the calculated mass 231 andthe start mass 236 will be determined at step 288 by the number ofsuccessful iterations performed by the ESS 140. The applicablepercentage of the mass difference will be added or subtracted to thestart mass 236 to become the effective mass 233. The higher the numberof iterations the larger the percentage of the mass difference isapplied, at step 290, to the start mass 236 will be. If the iterationconditions at step 282 are still respected, a new iteration will occurand the cycle continues until the iteration conditions at step 282 arenot met. Various other logics could also be designed by someone havingskills in the art of programming an ESS 140 to achieve similar resultswithout departing from the scope of the present invention.

The mass of the vehicle 10 effects the vehicle's behaviour thus themagnitude and reaction time of an effective corrective measure. Letstake for example a vehicle having a mass X negotiating a curve at aspeed S and the same vehicle in the same curve at the same speed S butwith a more significant mass X+Y. The corrective measures of the formerare unlikely to be acceptable in the latter case because the mass of thevehicle is significantly increased. The corrective measures based on thevehicle of mass X is unlikely to apply a corrective measure fast enoughor with enough magnitude to keep the vehicle of mass X+Y stable, thusthe advantage of having a seat sensor 120 to tell the ECU 140 whichstart mass 234 or 236 to use. The opposite scenario is also preferred toavoid where the corrective measures are calculated using mass X+Y whenthe actual mass is X. This will cause the magnitude and reaction time tobe larger and shorter than needed thus having a negative effect on thevehicle performance. As illustrated in FIGS. 14 and 15, the outputs fromthe ESS 140 depend on the overall mass of the vehicle and mass appliedthereon. The heavier the vehicle 10, the faster and larger the ESScorrective measures must be to keep the vehicle 10 within a stablecondition. FIG. 14 shows that the brake pressure ramp-up speed is fasterwith a heavy vehicle 10 to provide timely interventions. This is why thepressure increase in the brake system is ramping-up faster. The oppositeaction, decreasing the pressure in the brake system, would also befaster with a heavy loaded vehicle 10. Referring to FIG. 15, theoperating brake pressure is also higher with a heavy-loaded vehicle toprovide sufficient braking force. A low operating brake pressure isinsufficient to provide the required braking force for a heavy loadedvehicle even if sufficient for braking a lightly loaded vehicle. Theengine 30 power output of the vehicle is also another parameter managedby the ESS either by altering the ignition, fuel injection, air intakeopening or limiting the maximum RPM.

It is contemplated that a quantitative mass of the vehicle can beobtained with additional sensors. With a quantitative mass, the ESS 140could select a more accurate calibration to determine the optimalcorrective measures. A suspension deflection sensor 122 or a strengthgage properly disposed on rightly selected structural parts of thevehicle 10 would provide quantitative data about the mass of the vehicleunder any load conditions. A quantitative mass evaluation is providingthe ESS with an accurate mass to determine the type and the magnitude ofthe corrective measures required to improve the handling and thebehaviour or the vehicle 10. In this case, it is likely that no massiterations would be needed although they could be used to ensure thatthe sensed mass is accurate.

A roll sensor 136 installed on the vehicle 10 determines a roll angle ofthe vehicle 10. The roll angle sensed by the roll sensor 136 is comparedto a pre-determined roll angle by the ESS 140. If the instant roll angleis above the pre-determined roll angle, the ESS 140 takes this rollangle into consideration. The pre-determined roll angle is set accordingto the mass of the vehicle 10. If the sensed roll angle is above thepredetermined roll angle it means the center of gravity of the totalmass of the vehicle and occupant(s) is higher than what is normallyexpected and the total mass of the vehicle and occupant(s) issignificantly heavier than the mass used by the ESS 140. In both cases,the ESS 140 will change the corrective measures to reduce the vehicle 10roll angle. The roll sensor 136 offers a simple way to provide a“reactive” investigation of the vehicle's behaviour. The ESS 140 cantherefore adjust the corrective measures if the real physical roll angleof the vehicle 10 is greater than the acceptable pre-determined rollangle.

It should be appreciated by those skilled in the art that modificationsand variations can be made to the embodiments of the invention set forthherein without departing from the scope and spirit of the invention asset forth in the appended claims and their equivalents.

What is claimed is:
 1. A method of controlling a three-wheeled vehicle,the three-wheeled vehicle comprising: a frame; three wheels attached tothe frame; and a straddle seat supported by the frame, the straddle-seatdefining a driver portion and a passenger portion adjacent to the driverportion, the method comprising: determining a state of a load sensorassociated with a portion of vehicle; selecting a first start mass whenthe load sensor is in a non-loaded state; selecting a second start masswhen the load sensor is in a loaded state: determining at least onevehicle parameter during operation of the vehicle; determining acalculated mass based at least in part on the at least one vehicleparameter; determining an effective mass based at least in part on thecalculated mass and a selected one of the first and second start masses;defining an output of an electronic stability system of the vehiclebased at least in part on the effective mass; and controlling astability of the vehicle using the output of the electronic stabilitysystem.
 2. The method of claim 1, wherein: the first start mass is basedon a driver-and-vehicle combined mass; and the second start mass is baseone a driver-and-passenger-and-vehicle combined mass.
 3. The method ofclaim 1, wherein determining the at least one vehicle parameter duringoperation of the vehicle includes determining an acceleration of thevehicle.
 4. The method of claim 3, wherein determining the accelerationof the vehicle includes obtaining the acceleration of the vehicle from alongitudinal accelerometer of the vehicle.
 5. The method of claim 3,wherein determining the at least one vehicle parameter during operationof the vehicle further includes determining a torque provided by anengine of the vehicle; and the calculated mass is determined based onthe acceleration of the vehicle and the torque provided by the engine.6. The method of claim 3, wherein the calculated and effective massesare not determined when the acceleration of the vehicle is outside of apredetermined range.
 7. The method of claim 1, wherein determining theat least one vehicle parameter during operation of the vehicle includesdetermining a torque provided by an engine of the vehicle.
 8. The methodof claim 7, wherein determining the torque provided by the engine of thevehicle includes: obtaining a degree of throttle opening from a throttleposition sensor; and obtaining a speed of the engine from an enginespeed sensor.
 9. The method of claim 1, wherein determining the at leastone vehicle parameter during operation of the vehicle includesdetermining a deceleration of the vehicle.
 10. The method of claim 9,wherein determining the deceleration of the vehicle includes obtainingthe deceleration of the vehicle from a longitudinal accelerometer of thevehicle.
 11. The method of claim 9, wherein determining the at least onevehicle parameter during operation of the vehicle further includesdetermining a brake torque; and the calculated mass is determined basedon the deceleration of the vehicle and the brake torque.
 12. The methodof claim 9, wherein the calculated and effective masses are notdetermined when the deceleration of the vehicle is outside of apredetermined range.
 13. The method of claim 1, wherein determining theat least one vehicle parameter during operation of the vehicle includesdetermining a brake torque.
 14. The method of claim 13, whereindetermining the brake torque includes obtaining a brake pressure from abrake pressure sensor.
 15. The method of claim 1, further comprisingdetermining if the vehicle is turning; and wherein the calculated andeffective masses are not determined when the vehicle is turning.
 16. Themethod of claim 15, wherein determining if the vehicle is turning isbased on an input from a steering angle sensor.
 17. The method of claim1, wherein determining the effective mass includes: determining adifference between the calculated mass and the selected one of the firstand second start masses: determining a percentage of the difference tobe applied to the selected one of the first and second start masses;adding the percentage of the difference to the selected one of the firstand second start masses when the calculated mass is greater than theselected one of the first and second start masses; and subtracting thepercentage of the difference from the selected one of the first andsecond start masses when the calculated mass is smaller than theselected one of the first and second start masses.
 18. The method ofclaim 17, further comprising repeating the steps of determining the atleast one vehicle parameter, the calculated mass and the effective massover a number of iterations; wherein the percentage of the difference tobe applied to the selected one of the first and second start massesincreases as the number of iterations increases.
 19. The method of claim1, further comprising validating the state of the load sensor when theload sensor is determined to be in a loaded state by applying a delayafter the load sensor is determined to be in a loaded state.